1. Field
The present invention relates generally to capillary seals, and more particularly to capillary seals used between relatively rotating components in a fluid dynamic bearing system.
2. Description of Related Art
Magnetic disc drives are used for magnetically storing information. In a magnetic disc drive, a magnetic disc rotates at high speed and a transducing head “flies” over a surface of the disc. This transducing head records information on the disc surface by impressing a magnetic field on the disc. Information is read back using the head by detecting magnetization of the disc surface. The transducing head is moved radially across the surface of the disc so that different data tracks can be read back.
Over the years, storage density has tended to increase and the size of the storage system has tended to decrease. This trend has led to greater precision and lower tolerance in the manufacturing and operating of magnetic storage discs. For example, to achieve increased storage densities the transducing head must be placed increasingly close to the surface of the storage disc. This proximity requires that the disc rotate substantially in a single plane. A slight wobble or run-out in disc rotation can cause the surface of the disc to contact the transducing head. This is known as a “crash” and can damage the transducing head and surface of the storage disc resulting in loss of data.
From the foregoing discussion, it can be seen that the stability of the rotating member supporting the storage disc at one or more bearing regions with respect to a stationary member is of critical importance. One bearing design is a fluid dynamic bearing. A fluid dynamic bearing includes a bearing region formed in a gap between a fixed and a rotating member, and a lubricating liquid disposed in the gap. Fluid dynamic bearings spread the bearing interface over a large continuous surface area in comparison with a ball bearing assembly, which comprises a series of point interfaces. A larger continuous surface area reduces wobble between the rotating and fixed members.
Motors employing fluid dynamic bearings typically are open at one or more ends of the motor. To keep the lubricating liquid in the bearing region, motors include various sealing mechanisms, such as capillary seals for retaining the lubricating liquid in the bearing region during non-operation of the motor. A capillary seal typically comprises two relatively angled surfaces at the end of the gap containing the bearing region. Capillary seals may lose fluid if subject to sudden jarring. Sudden jarring can be avoided in some environments. However if disk drives having fluid dynamic bearings and capillary seals are to be used in more rugged environments, such as handheld devices, further precautions to prevent lubricating liquid loss from a capillary seal may be required.